The present invention is directed to methods and apparatus for logging and permanently monitoring subsea oil, gas, and injection wells; specifically to deploying photonic, electromagnetic or hydraulic conduits in an alternative path adjacent the production tubing in said wells.
Subsea wells are broadly defined as wells that do not provide fixed access from the surface of the sea. Subsea wells have wellheads located at or very near the sea floor and produce into subsea pipelines or provide access only through long subsea umbilical cables to distant locations. Traditional offshore wells located on offshore platforms have wellheads located on the a platform at or above the sea surface.
Fluid flowing from subsea wells proceeds out of the wellbore from one or more producing zones, through a system of continuous conduits, subsea wellheads, subsea flow lines and subsea pipelines to a surface production and storage facilities. Often, the well products have to travel many miles from the location of the subsea well head to such storage facilities.
As oil and gas becomes more and more difficult to find on land or in shallow coastal waters, the oil and gas industry has commenced exploration and development in deeper waters, miles from production and storage facilities. Prior to oil and gas being discovered in deep waters, the preferred method of producing the wells was to place the wellheads and the subsequent control devices for the wells at the sea surface on a platform. The access to these wells for the purpose of placing monitoring devices or performing intervention logging services was easily performed from the off-shore platform with the many well known methods of wireline logging, continuous coiled tubing, or even hydraulically pump down logging and monitoring systems.
Obtaining access to subsea wells for logging, monitoring or control purposes generally requires a costly submersible connection from the sea surface to the wellhead. Current methods, for example, to repair permanently disposed monitoring equipment, or to insert a suite of well logging tools into subsea wells, require the mobilization of a surface vessel which contains an off shore rig known to those in the industry as a semi-submersible rig or a drill ship. In all cases, the entry into the subsea well of the logging tools or tools to replace and dispose permanent monitoring equipment is performed through the production tubing. Because such wells are very expensive to drill and bring on line, most oil and gas producers prefer to not reenter the well unless absolutely necessary.
Hence, subsea wells are difficult to log or access for the placement of monitoring equipment. Further, visual inspections of these subsea wells are impossible because of the depths and distances of the wellhead from the nearest maintenance and production platform facility. Abnormal subsea well conditions cannot be observed in the manner of offshore platform wells or land wells, where pressureu gauges and visual leak detection may be maintained.
Monitoring of the subsea wells for safety, reservoir evaluation, and environmental reasons requires the instrumentation monitoring of the subsea well to be done remotely. This requires the transmission of the data from subterranean sensors in the well and subsea monitoring sensors over large distances to a receiving and processing node. This transmission of data is normally done over copper or optic fiber transmission umbilicals connecting the subsea wells back to surface data receiving stations. Because of the long distances and depths, considerable expense must be incurred to utilize these subsea umbilicals.
Furthermore, the current monitoring methods to monitor subsea wells are further compromised by the frequent failure of various subterranean gauges and instruments used to monitor oil and gas wells. Because of the remoteness of subsea wells from the surface of the sea and the need for rig interventions to access the subsea and subterranean monitoring devices, they require well maintenance to be performed from intervention rigs which are not always immediately available to perform such maintenance. The result of these failures and the difficulty of quickly repairing them generally results in the decision to continue producing deep-water wells without any subsea monitoring information for leaks and pressure anomalies and without subterranean monitoring of reservoir parameters. Such shortcuts are undesirable because they can lead to catastrophic failures of wells, hydrocarbon releases into the sea, and less than optimal reserve recovery.
The logging of wells has traditionally been done from platforms and on land wells to obtain additional information about a well""s reservoir condition and the integrity of the well""s structure. In subsea wells, logging is rarely done, as it requires the mobilization of very large and expensive semi-submersible rigs or drill ships. Furthermore, these subsea logging interventions introduce the possibility of losing wireline equipment in the well and compromising the well""s ability to produce. Also, subsea logging operations normally require the production of the well be reduced or curtailed during process of rigging up of the logging equipment.
Because of the above-mentioned difficulties of logging and maintaining unreliable subterranean monitoring equipment and very long umbilical transmission lines, many subsea wells are produced while monitoring the produced fluid back at the process or storage facility many miles away. This method of monitoring does not yield any indication of where the fluids are coming from in the well (i.e. which portion of the formation may be producing) which may be desired where production may be resulting from large perforated intervals in the well. Additionally, flow rate information monitored at the surface does not identify possible cross flow of fluids between reservoir intervals, changes in water, oil, and gas quantities as function of the depth of the well, the presence of leaks in well tubular conduits, and whether the reservoir is depleting in pressure.
It is desirable from both a reservoir engineering perspective as well as from a safety and environmental perspective to obtain real-time information from subsea wells relating to dynamic subterranean environment, fluid production parameters, and subsea well equipment integrity. Examples of parameters which are desirable to monitor on a real-time basis are fluid flow rates, water cut, resistivity of subterranean formations, spontaneous potential of subterranean reservoirs, pressure, temperature, sand production, steel wall thickness of tubulars, seismic energy from the reservoir or other sources, and other variables known to those familiar with oil and gas production. This information is currently gathered from either permanently disposed monitoring devices attached to the production tubing or from well intervention methods that insert the devices concentrically through the production tubing in the subsea well.
The commonly disposed permanent monitoring devices include pressure sensors, flow meters, temperature sensors, geophones, accelerometers, seismic source broadcasters, and other sensors and instruments. These devices are inserted in subsea wells concentrically through the well""s production tubing either using wireline, coiled tubing, and slickline, from a rig placed at the surface of the sea and connecting to the subsea well through the water by risers. Alternatively, these permanently disposed devices are inserted in a well with the production tubing. The production tubing is also inserted into the well via the use a rig on the surface of the sea where again a large riser is run from the subsea wellhead at the sea floor up through the water to the rig. Therefore, when permanently disposed monitoring equipment is inserted in a well either with production tubing or the other forms of insertion of the devices concentrically through the production tubing, a surface rig is required.
All of these parameters are obtained traditionally on land or offshore platform wells using offshore platform wells via the art of well logging. However, in the case of subsea wells the methods have to date not been developed to allow for safe, simple, and rapid log intervention into wells. Likewise, the retrieval of down hole pressure gauges or other instruments on land or offshore platform wells is often achieved by a well intervention with commonly known methods of wire line operations thereby not requiring a rig to be mobilized to the land or offshore platform location. Failure and need for retrieval of subterranean pressure gauges or other subterranean instruments in subsea wells can not be performed by wire line or logging interventions unless a semi-submersible rig or drill ship is deployed to the subsea well location. The present invention provides a rigless intervention method to access subsea wells.
Several subterranean data gathering systems are currently used to obtain data from the wells. This is commonly done using down hole permanent pressure gauges, and flow meters, that have long umbilical from the subsea well to a platform or floating production facility. The umbilical have electrical or optical cable to transmit data from the different permanently deployed instruments and devices in the well. The current method of gathering data from subsea wells practiced by the oil and gas industry requires the pressure gauges and pressure gauge electrical or optical data transmission line be disposed in the subsea well during the initial well construction, known to those familiar with the art as the well completions. It also requires that all down hole instruments be connected to data transmission lines, either electrical or optical lines, by a subsea wet connection. This connection then connects the subterranean data transmission lines to the subsea umbilical transmission lines. These connections are difficult to do at deep-water depths, which often have large currents, high hydrostatic pressures, and are at depths where only a very limited number of Remotely Operated Vehicles (ROVs) can operate and make such wet connections.
The deep-water wells are being placed further from land, platforms, or floating process facilities to which the umbilicals are connected. This results in very long umbilicals with large weights and costs. Therefore, each additional instrument data transmission requirement from the subsea well requires an additional line in the umbilical going from the subsea wellhead back to the host facility at the sea surface often many miles away.
When the pressure gauge fails or when the data transmission line fails, or when the data transmission""s wetmateable connection fails, the only recourse for repair of the data gathering system is an intervention into the well, using either a drill ship or a semi-submersible drilling rig resulting in the pulling of the well completion, and a significant number of days of lost production during the recompletion of the well, all as previously described.
The present invention provides a method and apparatus to intervene into these deepwater subsea wells without deploying a deepwater rig to hydraulically connect to the subsea wellhead and thereafter deploy logging instruments into the well has long been sought by the oil and gas industry. Another feature of the present invention permits the entry of subsea wells for the purpose of obtaining data without placing logging tools and wire line cable into the production tubing fluid flow stream of these subsea wells. The intrusion of logging tools into the flow stream of such wells presents a significant risk of losing the logging equipment in the well and obstructing fluid production. The present invention obviates the need for such interventions.
A new method of logging, monitoring and controlling subsea oil and gas wells is provided. This invention describes a method and apparatus to obtain continuous or periodic data (if desired) from reservoirs producing through subsea wells. This invention further describes the method and apparatus used to process, transmit, and archive said data into information for reservoir and well management. The present invention relates to a new method and apparatus for constructing subsea wells using an alternative path conduit to connect the subterranean conduit to a submersible conduit proceeding from the wellhead to the surface of the sea.
The preferred embodiment of this invention consists of a dual conduit system with the dual conduits connected at the bottom in the well providing a U-connection at the ends of the dual conduit and the other ends proceeding through the well head terminating outside the well head in a pair of hydraulic wet connection devices. This then forms a continuous conduit starting at the sea floor near the sub-well down the well and then back up to the subsea surface outside the well terminating in the two sea floor hydraulic wetmate devices.
This invention further teaches the method of constructing a well by placing the alternative path conduits into one of the subsea wells casing conduits. This invention teaches the insertion of logging tools, instruments, wireline, optic fibers, electrical cable, and other tools and instruments through the inventions alternative path conduits. This alternative path tube is deployed in the well, proceeds upwards through the wellhead, subsea safety valves, through subsea hydraulic disconnects, and to the sea surface, where it can be accessed by surface service vessels which can deploy logging tools and other instruments into the alternative path. The invention further teaches the method of inserting permanent subsea and subterranean monitoring devices through the alternative path conduits of this invention.
This invention further teaches the connection of the alternative path conduits to a surface instrument pod by connecting continuous conduit from the conduit proceed forth from the sub sea well and wellhead terminating at the hydraulic wet connects, where the inventions surface instrument pod remains on station above the subsea well at the sea surface. The invention further teaches that the instrument pod can have recording, processing and transmission devices inside the pod where the devices record, processes, and transmits the data and information to receiving locations on land or offshore. The use of an umbilical connected back to a remote surface instrument pod from the alternative path conduit disposed in the subsea well avoids the need for long umbilical cables back along the sea floor to the host production facility miles from the subsea well. An additional feature of this invention permits remote data transmission and well interaction. Commands can be transmitted from a remote station to the surface instrument pod, and then down the umbilical disposed in the sea, and into to the subsea well for the purpose of operating downhole devices, such as valves, gauges, sensors and the like in response to these remote commands.